Cathode materials for secondary batteries

Abstract

A cathode active material includes a composition expressed as:Li1+β(NixMnyCoz)M1α(Nix′Mny′Coz′)M21−αO2; orNa1+β(NixMnyCoz)M1α(Nix′Mny′Coz′)M21−αO2;where: M1 represents a core composition comprising of Ni, Mn, and/or Co or a combination of at two of thereof; M2 represents a surface composition having at least 50% Co, and, optionally Ni and/or Mn; the structure of M2 may be a composite structure and includes a rock-salt or disordered rock-salt phase; 0.5≤α<1, 0≤x≤1, 0≤y≤0.5, 0≤z≤1, 0≤x′≤0.5, 0≤y′≤0.5, 0.5≤z′≤1, and −0.1≤β≤0.1; the sum of x, y and z is 0.9-1.1, and the sum of x′, y′ and z′ is 0.9-1.1.

What is claimed is: 
     
         1 . A process of preparing a cathode active material, the process comprising:
 providing a first aqueous metal ion solution;   providing a second aqueous metal ion solution;   combining the first aqueous metal ion solution with the second aqueous metal ion solution and with a precipitating agent to form a precipitate;   isolating the precipitate;   mixing the precipitate with a lithium or a sodium salt to form a mixture; and   heating-treating the mixture to form the cathode active material that is expressed as:
 a core portion comprising: Li 1+β (Ni x Mn y Co z ) M1 O 2 ; and a surface portion comprising Li 1+β′ (Ni x′ Mn y′ Co z′ ) M2 O 2 ; or 
 a core portion comprising Na 1+β (Ni x Mn y Co z ) M1 O 2  and a surface portion comprising Na 1+β′ (Ni x′ Mn y′ Co z′ ) M2 O 2 ; 
 wherein:
 the cathode active material comprises particles having a generally spherical morphology and a vector radius defined from a core of each particle to the surface of each particle; 
 the surface composition comprises at least 50% Co; 
 a structure of composite M2 comprises a disordered rock-salt phase; 
 0≤x≤1, 0≤y≤0.5, 0≤z≤0.4, 0≤x′≤0.5, 0≤y′≤0.5, 0.5<z′≤1, −0.1≤β<0.1 and −0.1≤β′<0.1; 
 the sum of x, y, and z is 0.9-1.1, and the sum of x′, y′, and z′ is 0.9-1.1; 
 the Ni concentration continuously decreases along the vector radius of each particle; 
 the Mn concentration continuously decreases along the vector radius of each particle; and 
 the Co concentration continuously increases along the vector radius of each particle. 
 
   
     
     
         2 . The process of  claim 1 , wherein:
 the heat-treating comprises at least one calcination step at a heating rate to a temperature of about 680° C. to about 1200° C.   the calcination step is conducted in an oxygen atmosphere, an air atmosphere, or in an oxygen-enriched air atmosphere.   
     
     
         3 . The process of  claim 1 , wherein 0.6≤x≤1, 0≤y≤0.4, 0≤z≤0.4, 0≤x′≤0.5, 0≤y′≤0.5, and 0.6<z′≤1. 
     
     
         4 . The process of  claim 1 , wherein composite structure M2 comprises from about 60 mol % to about 90 mol % Co. 
     
     
         5 . The process of  claim 1 , wherein composite structure M1 has a layered structure and/or a spinel structure. 
     
     
         6 . The process of  claim 1 , wherein the concentration of any metals changes by one or more slopes. 
     
     
         7 . The process of  claim 1  further comprising a dopant cation. 
     
     
         8 . The process of  claim 1  further comprising a surface coating on the particle. 
     
     
         9 . The process of  claim 8 , wherein the surface coating comprises a metal oxide, a metal fluoride, a metal phosphate, a conductive carbon coating, a conductive polymer, or a combination of any two or more thereof. 
     
     
         10 . The process of  claim 9 , wherein the surface coating comprises a conductive polymer comprising poly(3,4-ethylenedioxythiophene). 
     
     
         11 . A process of preparing a cathode active material, the process comprising:
 providing a first aqueous metal ion solution;   providing a second aqueous metal ion solution;   combining the first aqueous metal ion solution with the second aqueous metal ion solution and with a precipitating agent to form a precipitate;   isolating the precipitate;   mixing the precipitate with a lithium or a sodium salt to form a mixture; and   heating-treating the mixture to form the cathode active material that is expressed as:
 a core portion comprising: Li 1+β (Ni x Mn y Co z ) M1 O 2  and a surface portion comprising Li 1+β′ (Ni x′ Mn y′ Co z′ ) M2 O 2 ; or 
 a core portion comprising Na 1+β (Ni x Mn y Co z ) M1 O 2  and a surface portion comprising Na 1+β′ (Ni x′ Mn y′ Co z′ ) M2 O 2 ; 
 wherein:
 the cathode active material comprises particles having a generally spherical morphology and a vector radius defined from a core of each particle to the surface of each particle; 
 the surface composition comprises from about 60% Co to about 90 mol % Co; 
 a structure of composite M2 comprises a disordered rock-salt phase; 
 0<x≤1, 0<y≤0.5, 0≤z≤0.4, 0≤x′≤0.5, 0≤y′≤0.5, 0.5<z′≤1, −0.1≤β<0.1 and 0<β′<0.1; 
 the sum of x, y, and z is 0.9-1.1, and the sum of x′, y′ and z′ is 0.9-1.1; 
 the Ni concentration continuously decreases along the vector radius of each particle; 
 the Mn concentration continuously decreases along the vector radius of each particle; and 
 the Co concentration continuously increases along the vector radius of each particle. 
 
   
     
     
         12 . The process of  claim 11 , wherein:
 the heat-treating comprises at least one calcination step at a heating rate to a temperature of about 680° C. to about 1200° C.   the calcination step is conducted in an oxygen atmosphere, an air atmosphere, or in an oxygen-enriched air atmosphere.   
     
     
         13 . The process of  claim 11 , wherein 0.6≤x≤1, 0<y≤0.4, 0≤z≤0.4, 0≤x′≤0.5, 0≤y′≤0.5, and 0.6<z′≤1. 
     
     
         14 . The process of  claim 11 , wherein composite structure M2 comprises from about 60 mol % to about 90 mol % Co. 
     
     
         15 . The process of  claim 11 , wherein in the composite structure M1 has a layered structure and/or a spinel structure. 
     
     
         16 . The process of  claim 11 , wherein the concentration of any metals changes by one or more slopes. 
     
     
         17 . The process of  claim 11  further comprising a dopant cation. 
     
     
         18 . The process of  claim 11  further comprising a surface coating on the particle. 
     
     
         19 . The process of  claim 18 , wherein the surface coating comprises a metal oxide, a metal fluoride, a metal phosphate, a conductive carbon coating, a conductive polymer, or a combination of any two or more thereof. 
     
     
         20 . The process of  claim 19 , wherein the surface coating comprises a conductive polymer comprising poly(3,4-ethylenedioxythiophene).